Mod_perl incorporates a Perl interpreter into the Apache web server,
so that the Apache web server can directly execute Perl code.
Mod_perl links the Perl runtime library into the Apache web server and
provides an object-oriented Perl interface for Apache's C language
API. The end result is a quicker CGI script turnaround process, since
no external Perl interpreter has to be started.

To tell Apache to load it, you'll have to put the following line 
somewhere into /etc/httpd/httpd.conf:
  Include /etc/httpd/mod_perl.conf
